Microstructure and mechanical properties of squeeze cast and semi-solid cast Mg-Al alloys

摘要

Magnesium-aluminium castings produced by means of squeeze casting, new rheocasting and thixocasting have been investigated. These casting processes provide very different microstructures consisting of alpha-Mg and beta-Mg_(17)Al_(12). The shape and distribution of the brittle beta-Mg_(17)Al_(12) has a large influence on mechanical properties. Isolated particles of beta-phase in squeeze cast components are less detrimental to ductility than the continuous beta-phase network found in semi-solid processed parts. A heat treatment results in complete dissolution of beta-Mg_(17)Al_(12) and accounts for significant improvements of ductility and fracture toughness. Crack propagation in solution heat treated Mg-Al castings is associated with extensive twinning.